A conventional toilet, when installed, is bolted to a flange which is in turn attached to the floor. The flange, which is commonly referred to as a "closet" or "toilet" flange, serves as a means for mounting the toilet and connecting the toilet to a drain pipe which leads to a sewer pipe.
It is usually required during construction to perform an air test or a water test of the plumbing to ensure that the pipes, fittings and the like are properly connected and don't leak. Although the pressures used in such testing are relatively low, the various means used in the past to seal the open tops of the most widely used prior art toilet flanges could be "blown-out" thus requiring resealing and retesting.
It is now common to make plumbing piping, such as drain pipe, and fittings, such as elbows, toilet flanges, and the like, of plastic materials, such as acrylonitrile-butadiene-styrene (ABS) or polyvinylchloride (PVC).
One type of prior art toilet flange which is molded of plastic has an integral knock out element which is positioned below the top of the inlet end of the flange immediately above the drain pipe connection. The knock out element closes off flow from the drain pipe through the flange and enables the water and air tests to be conducted with the flange in place. However, this flange had a distinct disadvantage. Once the air or water tests are conducted, and the knock out element is removed by a blow or blows of a hammer, the knock out element which is smaller than the lumen of the drain pipe can fall down into the drain pipe causing problems.
It would be advantageous to have a molded plastic toilet flange that did not possess the disadvantages of prior art flanges.